The present invention relates to a solid-state imaging apparatus, a signal processing method and, a camera, and particularly to technology that performs both color imaging using visible light and imaging using infrared light at high resolution.
Conventionally, a solid-state imaging apparatus used for a digital still camera and a digital video camera obtains a color image using three primary color filters (a red filter, a green filter and a blue filter) or four complementary color filters (a cyan filter, a magenta filter, a yellow filter and a green filter).
When incident light that has passed through a filter is received by a photodiode, the photodiode receives light in a wavelength region (around 380 nm to 1100 nm) which is wider than the visible region of humans (around 380 nm to 780 nm) to generate signal charge. This gives an error of infrared light, deteriorating color reproducibility. Thus, it is common to remove infrared light in advance using an infrared cut filter (herein after, “IR cut filter”). However, the IR cut filter decreases visible light by about 10 to 20 percent, which deteriorates the sensitivity of a solid-state imaging apparatus, degrading an image quality.
In order to solve the above problem, recently, a solid-state imaging apparatus in which no IR cut filter has been proposed (see Patent Document 1). FIG. 1 is a circuit diagram showing a main structure of a solid-state imaging apparatus that pertains to conventional technology and that detects infrared light in addition to visible light.
As shown in FIG. 1, a solid-state imaging apparatus 11 includes pixels 1101, a vertical shift register 1102, vertical signal lines 1103, row memories 1104, a horizontal shift register 1105, a horizontal signal line 1106 and an output amplifier 1107. Each of the pixels 1101 has an individual filter. Filters are arranged such that units of arrangement, in each of which four filters are squarely arranged like a unit of arrangement 1108, are two-dimensionally arranged. Here, the four filters are a filter that mainly transmits red light (herein after, “red filter”) (R), a filter that mainly transmits green light (herein after, “green filter”) (G), a filter that mainly transmits blue light (herein after, “blue filter”) (B) and a filter that mainly transmits infrared light (herein after, “infrared filter”) (IR).
The pixels 1101 selected by the vertical shift register 1102 transfer pixel signals to the row memories 1104 via the vertical signal lines 1103. After the pixel signals stored in the row memories 1104 are selected one at a time by the horizontal shift register 1105, the pixel signals pass through the horizontal signal line 1106, are amplified in the output amplifier 1107 and then are outputted.
Then, the output signals of the pixels 1101 that have received red light, green light and blue light are corrected using the output signals of the pixels 1101 that have received infrared light.
Thus, it is possible to achieve high color reproducibility without using the IR filter.    Patent Document 1: Japanese Laid-open publication No. 2005-184690    Patent Document 2: Japanese Laid-open publication No. 2002-142228    Patent Document 3: Japanese Laid-open publication No. 2000-059798
However, according to the solid-state imaging apparatus 11, a row where as much as half of the pixels detect infrared light is in every other row. Also, a column where as much as half of the pixels detect infrared light is in every other column. Therefore, information about visible light is insufficient in rows and columns where the number of pixels that detect infrared light is large, deteriorating resolution.
In order to solve such problem, for example, it is possible to prevent information about visible light from being insufficient, using a filter that transmits light in a predetermined wavelength region in addition to infrared light like a solid-state imaging apparatus disclosed in Patent Document 2.
However, it is necessary to laminate a plurality of filters in order to obtain a filter disclosed in Patent Document 2, which prevents a solid-state imaging apparatus from being downsized and also is against a request for increasing a pixel count. Also, complex operations are needed for obtaining a pixel signal of each three of the primary colors, making the solid-state imaging apparatus impractical.
Also, it is needless to say that it is desirable that such solid-state imaging apparatus is able to perform both color imaging using visible light and imaging using infrared light. Also, it is needless to say that it is desirable that both color imaging and imaging are performed at high resolution. However, according to a solid-state imaging apparatus disclosed in Patent Document 3, for example, since filters are switched each time (i.e. in performing color imaging using visible light and in performing imaging using infrared light), it is not possible to perform both color imaging and imaging at the same time.